In recent years, nuclear medicine imaging apparatuses, such as a gamma camera, a single photon emission computed tomography (SPECT) apparatus, and a positron emission tomography (PET) apparatus, have been known. The nuclear medicine imaging apparatus includes a detector that detects radiation. The nuclear medicine imaging apparatus detects radiation emitted from an isotope or a labeled compound which is introduced into body tissues using the detector and forms the image of the dose distribution of the radiation detected by the detector, thereby reconstructing a nuclear medicine image that provides the functional information of the body tissues.
For example, a radioactive drug including a labeled compound that is frequently introduced into tumor tissues is put into the body of the examinee. Then, the nuclear medicine imaging apparatus detects radiation emitted from the labeled compound for a predetermined period of time and reconstructs a nuclear medicine image including the distribution of the tumor tissues of the examinee into which the labeled compound is introduced, thereby providing the functional information of the body tissues of the examinee.
In addition, in recent years, apparatuses have been proposed in which a nuclear medicine imaging apparatus that provides functional information is integrated with an X-ray computed tomography (X-ray CT) apparatus that provides shape information. For example, the following apparatuses have been proposed: a PET-CT apparatus in which a PET apparatus and an X-ray CT apparatus are integrated with each other; and a SPECT-CT apparatus in which a SPECT apparatus and an X-ray CT apparatus are integrated with each other.
However, in the above-mentioned technique, in some cases, the image quality of a region of interest is lower than that of other regions in the PET image.